Monitoring ablation growth and determining treatment efficacy has become one of the most significant challenges facing thermal tumor ablation. Post-ablation imaging provides no way to monitor the ablation as it develops and current real time strategies fail to provide sufficient spatial resolution of the ablation zone. Without a means to monitor ablation growth, there is no way to prevent unintended thermal damage before it occurs, nor is it possible to alter the course of treatment at the most effective times. In this application, we will begin to develop, optimize and validate a new treatment monitoring technique using technology already available on most scanners using periodic contrast-enhanced computed- tomography (CECT). Periodic CECT will allow monitoring at several time points during the course of treatment while minimizing the total contrast load to the patient. Specifically, we propose to: 1. Measure the uptake and transport of contrast media during thermal ablation Here we will measure the retention or expulsion of contrast media in normal liver and kidney, and two tumor models during ablation. 2. Optimize administration of contrast media and image acquisition parameters for ablation monitoring with periodic CECT In this aim we will characterize periodic CECT during thermal ablation and optimize scan timing, radiation dose and contrast infusion rate using simplex methods. 3. Automate HYPR processing for periodic CECT ablation monitoring. This aim will focus on developing applicator discovery, block matching and registration algorithms to facilitate automated HYPR processing during each imaging sequence. 4. Validate the periodic CECT technique with histopathology and standard CECT In this aim the validity of periodic CECT will be verified by comparing the imaging appearance and histopathology of ablations created in normal liver and kidney, and two tumor models.